The term "grout" is commonly applied to the thin, wet mortar which is pourable and used for filling structural gaps such as the joints between units of masonry, tile, brick or stone used to cover household and institutional surfaces, e.g. in bathrooms, kitchens, terraces and the like. Grout is usually formed of a mixture of cement, lime or gypsum plaster, with sand and enough water to render the mixture flowable and plastic. The wet grout is then pressed into the joints or gaps between the tiles and allowed to harden so as to form a connective matrix between the individual tiles.
Although the initial plasticity of the grout renders it easy to handle, the evaporation of the water from the grout which occurs during the hardening process leaves a open crystalline matrix which renders the body of the grout porous and which readily absorbs environmental pollutants such as cooking fat, tobacco smoke, body oils, exhaust fumes and the like. Besides discoloring the grout and rendering it unattractive, the acidic components of these soils also weaken the cyrstalline matrix of the grout thus further increasing its porousity which in turn speeds the discoloration and decomposition processes already begun.
Compositions intended to renew the discolored or damaged surface of grout have generally fallen into two classes. The first class of compositions intended to clean grout use harsh acids, such as hydrochloric acid, which, while they may be effective to remove the alkaline soils, also dissolve a portion of the basic grout matrix during the cleaning process and further increase its porousity.
A second class of compositions include those such as colored chalks or pastes which are spread over the surface of the grout and are intended to recolor it. Such compositions neither clean the grout nor repair the damaged matrix of the grout and at best offer only a temporary solution to the discoloration of the grout.
One approach to recoloring discolored or stained grout is found in U.S. Pat. No. 4,130,442 which discloses applying to the grout a pigmented polymeric dispersion which forms a water resistant coating on the grout. Although this patent discloses a method to color the surface of discolored grout, it does not address the problem of corrosive pollutants absorbed into the body of the grout and the damage which results from exposure of the grout to such pollutants.
Therefore, a need exists for compositions which will counteract the damage caused by environmental pollutants, particularly those of acidic nature, and which also function to restore the color and texture of the surface of the grout to which they are applied.